Pilot Study of the Evaluation of Sirolimus in the Treatment of Diabetic Macular Edema This study will test whether sirolimus, a drug approved to treat psoriasis and other conditions, can help patients with diabetic macular edema. In this disorder, blood vessels in the retina (a thin layer of tissue that lines the back of the eye) become leaky and the retina swells. The macula, the center part of the retina that is responsible for fine vision, may also swell and cause vision loss. Sirolimus inhibits a protein in the body called mTOR, which plays a critical role in regulating how cells divide and grow. Sirolimus is also believed to affect the inflammatory process. For both these reasons, the drug may be helpful in treating diabetic macular edema